See Also

Apple has revealed that content will move in the same direction as your finger when scrolling inside of Lion via your mouse or Magic Trackpad. You scroll down, you move up in your document.

This is exactly the opposite of how it's worked ever since the scroll-wheel mouse hit the market 16 years ago, Debates on how good or bad of an idea it is aside, here's how to bring that new functionality to Snow Leopard before getting your mitts on Lion.

Just install a free utility called Scroll Reverser. It adds an option in your menu to modify how your scroll wheel functions. Do you want content to scroll in the opposite direction or same direction as your finger? Then activate and deactivate Scroll Reverser.